Enameling apparatus



June 12', 1934, w. T. CHRISTMAN ET AL ENAMELING APPARATUS Original FiledMarch 11, 1927 INVENTORS 5 Sheets-Sheet l June 12, 1934.

w. T. CHRISTMAN '21" AL 1,962,635

ENAMELING APPARATUS Original Filed Ma rch-ll, 1927 5 Sheets-Sheet 2 I 1l 4 IIIIII/II INVENTOR5 w. T. cHms-rMAN ET AL 1,962,635

June- 12, 1934.

ENAMELING APPARATUS iginal Filed March 11, 1927 5 Sheets-Sheet 4 I ZaZaz 7m INVENTORS June 12, 1934. W CHRISTMAN 1,962,635

ENAMELING APPARATUS Original Filed March 11, 1927 5 Sheets-Sheet 5 3a-ILg13- Patented June 12, 1934 UNITED STATES ENALIELING APPARATUSWilliam T. Christman and Herbert Dean, McKees Rocks, Pa., assignors toThe Carborundum Company, Niagara Falls, N. Y., a corporation ofPennsylvania Continuation of application Serial No. 174,521, March 11,1927. This application March 23, 1928, Serial No. 264,169. RenewedJanuary 27,

, 27 Claims. (Cl.25142) This invention relates to furnace structures,and more particularly to an apparatus for the treatment of enamel ware,although it may obviously be used for other purposes. Enamel wareincludes a wide range of articles, such for instance, as culinaryutensils. Such articles are made of metal, usually steel, worked toshape and then coated. This application constitutes a continuation ofour copending application, Serial No. 174,521, filed Mar. 11, 1927.

Coating is effected by dipping the ware in a fluid preparation of asubstance, which at the proper temperature, will vitrify. After dipping,the article is gradually heated, first to dry the coating and then toefiect vitrification. The temperature at which the coating vitrifiesranges around l500 Fahrenheit and upwards.

In carrying out the invention, the articles are first dipped, thengradually advanced through a long chamber or through a succession ofchambers in which the coating is first partially dried, then heatedfurther to complete the drying, and then fired at a high temperature toproduce vitrification of the enamel. Beyond the region of vitrification,the articles gradually lose their heat and finally emerge from thechamber at a temperature such as to insure their safety against injury.

Our invention contemplates the provision of a simple form of apparatuswherein the drying and firing of the enamel coating may be economicallyand efficiently carried out, and wherein the articles, during thegreater portion of their travel may be shielded from exposure to theproducts of combustion. The invention further contemplates the provisionof a drying and heating apparatus wherein attendants may have access tothe articles between the steps of drying and firing for the purpose ofperforming such operations as may be necessary, as for instance, what isknown as beading.

The invention may be understood by reference to the accompanyingdrawings, in which Figure 1 is a top plan view of a heating furnaceembodying our invention;

Figure 2 is a vertical transverse section on a larger scale in the planeof line II-II of Figure 1;

Figure 3 is a transverse section through apart only of the structure inthe plane of line IIIIII of Figure 1;

Figure 4 is a diagrammatic view showing aplurality of drying and fusingchambers arranged in succession;

Figure 5 is another diagrammatic view showing a further modification offusing and drying chambers;

Figure 6 is a view showing in side elevation, a detail. portion of thestructure, showing the closure plates for the slot in the top of thefurnace;

Figure '7 is a detail view showing another arrangement for the guidesfor the hangers passing through the top of the furnace;

Figure 8 is another detail view of this arrange-- ment, the top of thefurnace being shown as being comprised of a suspended arch;

Figure 9 represents a transverse section through a furnace wherein thesupports for the articles to be baked extend upwardly through the bottomof the furnace instead of projecting down through the top thereof;

Figure 10 is a view similar to Figure 9 of a slightly modifiedarrangement;

Figure 11 is a diagrammatic plan view of an installation wherein hotgases of combustion are transferred from the furnace to the drier;

Figure 12 is a transverse vertical section through the installationshown in Figure 11 in substantially the plane of line XII---XII;

- Figure 13 is a similar section in the plane of line EHII-XIII ofFigure 11; and

Figure 14 is a side elevation of a portion of the conveyor showin amodified arrangement for the closure plates.

In the construction shown in Figures 1 to 3 of the drawings, there aretwo tunnel members, 1 and 2. These members extend horizontally side byside and are parallel. Located above the furnace structure is a conveyor3 which comprises an endless chain, or its equivalent, which passesaround sheaves 4 at each end of the apparatus, and which are driven byany suitable driving mechanism, not shown. The chain 3 is suspended fromhangers 3 and these hangers have rollers 3 thereon which engage in arunway 5 located above the top of the oven chamber. The direction oftravel of the chain is indicated by arrows in Figure 1. The sheaves 4are located in a plane above the top of the furnace structure, and atone end of the furnace they are preferably located a considerabledistance from the furnace structure so that the chain will have anappreciable travel after emerging from the discharge end of the chamber2 before re-entering the intake end of the chamber 1. At the other endof the furnace structure the chain preferably has less travel throughthe open, and in some cases, this portion of the chain might be entirelyenclosed, as will be readily understood.

Along the center of the top of the chambers 1 and 2 is a continuous slot6. Suspended from the I chain 3 at intervals are hangers 7 from whichthe ware is adapted to be hung, as showninjFigure 6. Pivotally carriedon each of the hangers 7 is a plate 12. These plates are rectangular andare of a heat resistant metal. Their width is such that they more thanspan the slot 6 in the top of the chambers l and 2, and they are of alength somewhat greater than the interval between successive hangers 7.7

The greater length of the plates is rearwardly of the pivot, so thateach plate, when free to do so, willtip slightly rearwardly from ahorizontal position to the inclined position shown in Figure, 6. Beingsomewhat longer than the interval between the hanger and beingidentically arranged, they overlap one another, as shown in Figure 6.The forward ends of these plates, with respect to the direction of theirtravel, are preferably upturned. Located along each side of the slot 6is a guide, which is preferably in the form of a pipe 11 through whichwater can be circulated to protect such guides or pipes from heat.Theplates 12 are located on the hangers 7 at just such height I thatthey will ride along the top of the pipes 11 with the forward end of oneplate raised on the rear end of the next plate. Inthis way the slotalong the top of the furnace is continuously closed by the overlappingplates 12. When the hangers are traveling free of the furnace structure,the plates 12 are hung free and do not interfere in any way with thefree operation of the chain.

In Figure 14 we have shown a modification of the arrangement of theclosure plates. In this figure, 7 designate rods depending from theconveyor (not shown), which rods are adapted to carry the ware, asillustrated in Figure 6. The closure plates are designated 12 A rod 7passes through the forward end of each plate, and the nextsucceeding-trod passes through the other end of the same plate, so thateach rod passes through the overlapping ends of two plates. The platesare free to slideup and down on the rods, but their downward movement islimited by pins 7 The pins are of less length than the width of the slotin the top of the furnace, so that they do not interfere with thepassage of the rods along the slot.

As the conveyor moves along the top of the furnace, the plates 12 canride along the guides and close the slot in the top of the furnace. Theplates do not prevent the conveyor from passing around the sheavesbecause the rods 7 are not rigidly connected to the plates, and thedistance between successive rods '7 is such that the plates 12 do notneed to be long enough to prevent the conveyor from making a sharp turn.

Instead of using water cooled pipes along the slot 6, steel guides maybe arranged along each side of the slot 6, as shown in Figure 7. Theseguides have inside'flanges 15 against which the hangers '7 may contact,and the flanges 15 will prevent the hangers from coming into contactwith the refractory material at each side of the slot. Each of theguides has an outer rail portion 15* on which the plates rest to closethe slot. The rails 15 may, for instance, be of a 27% chromium iron orother high temperature alloy, and can be used in installations where thetemperature is so high that water cooling would otherwise be necessary.This arrangement is particularly desirable where it is found that thecondensation of moisture and volatile constituents from the enamel takesplace on the water pipes and results in the corrosion of the latter.

move in the direction In some-installations it may be desirable to usewater pipes, and to provide a housing therefor. Such an arrangement isshow n in Figure 8 wherein there is a pipe 16 alongeach side of the slot6. Outside of each water pipe 16'is a guide rail or enclosing rail 17,such for instance, as a Z-bar. The 2 bars 17 enclose the pipes 16 aswell as the plates 12 on the hangers 7.

The inturned flanges 17 of these Z-bars form a guide for engaging thehangers 7 to prevent the hangers from scraping against the brick work orrefractory material forming the top of the furnace. In Figure 8 the topof the furnace, designated generally as 18, is a suspended archstructure. The provision of a suspended arch simplifies the constructionof the furnace where a slot longitudinally of the center ofth'e arch isrequired.

The tunnel 1 in the arrangement shown in Figures '1 to 3, inclusive is apreliminary drying and heating chamber. The temperature in this chamberis ordinarily so low that the water cooled pipes 11 could be omitted ifdesired, and in fact, for this part of the structure, the entire slottedarrangement could be omitted. tunnel 2 includes the fusing chamber wherethe temperature of the article is raised to a point sufficient to effectvitrification of the coating material. The articles to be treated arehung on the chain 3 prior to the entrance of the hanger into the chamber1 and at the right hand end of the apparatus, as viewed in Figure 1, andindicated by arrows in the drawings.

The tunnel member 1 may be provided with no heating elements, as, forinstance, gas burners 8, to afi'ord drying and heating conditions wheresuch an arrangement is considered desirable. These heaters 8, in theparticular construction shown where the overall length of the apparatusis about sixty feet, extend from a point about fifteen feet inwardlyfrom the intake of the tunnel member. 1 through substantially the entireremainder of the extent of this tunnel.

The volume of the flames, the size of the chamher, and the rate ofadvance are so correlated that the article is not merely thoroughlydried or baked, but is gradually and thoroughly heated to a temperaturesuited for its further progress.

The articles emerge. from'the tunnel 1, traveling from right to left, asviewed in Figure 1, and are carried around the entrance end of thetunnel member 2, the exposure to the open air in this portion of thetravel of the ware preferably being short as possible. If it is desiredto perform the operation known as beading in which some of the enamel isremoved from the bead of the ware after it has been coated anddried, inorder to prevent objectionable streaking or dripping, -it may be readilydone at this point where the ware travels through the open. Decorationof' the ware may also, if desired, be done at this point, for instance,by adding other glazes to form a pattern. If desired, however, thisportion of the conveyor might also be enclosed.

It has been previously pointed out that in the particular installationshown the tunnel 2is about sixty feet long. The tunnel 2 is dividedinto' 9 three .sections of approximately equal length, designated 2 2and 2. The middle section 2 is the heating section, and its structuremay be clearly understood by reference to Figure 2. At each side of thetunnel 2 is a combustion chamber which is formed in the side wall, thesefire boxes being designated 9. The exposed walls of the combustionchambers are preferably of a material which is a high conductor of heatand which is a good radiator of heat, such, for instance, as siliconcarbide.

At the bottom of the tunnel may be another combustion chamber or heatingflue 10. The fire boxes 9 and 10 are co-extensive or substantiallyco-extensive with the central section 2 of the furnace. Fuel is burnedin the combustion chambers 9, and if desired, in the flue 10, and theheat is radiated through the exposed walls into the tunnel, thetemperature in the tunnel being raised to a point sufficient to effectfusion or vitrification of the enamel coating material on the ware. Ifdesired, the gases of combustion may be discharged from the combustionchambers into the furnace so as to heat the ware both by radiation andby contact, in which case they would be carried through a stackspecially provided for the purpose.

No heating elements would ordinarily be provided in portions 2 and 2 ofthe tunnel, so that ware traveling through the tunnel 2 will first entera relatively cool zone, and move gradually toward the 'middle of thefurnace where a condition of maximum temperature will prevail. Where thebottom flue extends forwardly under the hearth of the preheating zone 2the ware is heated much more rapidly, and while this zone is relativelycool as compared with the fusing zone, it is, nevertheless, heated to avery considerable extent.

After passing the middle portion of the furnace, the heat will graduallyfall off toward the discharge end of the furnace.

The operation of the furnace may be explained with reference to Figurel. The burners or gas outlets within the tunnel member 1 provide meansfor heating the drying tunnel 1. At the same time the combustionchambers 9 and flue 10 are in operation and the conveyor 3 is in motion.

The attendants hang the articles which have been coated upon the hangers'7 at or near the point where the conveyor 3 advances to the tunnelmember 1. The travel of the conveyor is relatively slow and the removalof ware which has been fired can easily be effected by attendantsworking at the same end of the furnace as the attendants who hung theware on the conveyor.

The articles advance through the tunnel mem-' ber 1 and as they advancethey are thoroughly dried and baked and become heated throughout.

Emerging from the tunnel member 1 at the left, they follow the turn ofthe conveyor 3 and with such intermediate exposure to the air as may bedesired. As previously explained, they then enter the chamber 2 wherethe ware moves from left to right, first through a region of graduallyin creasing temperature to a zone of maximum temperature where itremains for a sufficient time for fusion to be effected. It then travelsthrough a region of gradually diminishing temperature until it finallyemerges at the right hand end of tunnel member 2 at a temperaturesufficiently low to allow exposure to the atmosphere without injury.

In place of gas burners for heating the drying chamber, it is, as ageneral rule, more satisfactory and more economical to heat the dryingtunnel with hot waste gases from the furnace. Such an arrangement isillustrated in Figures 11, 12 and 13. In these figures, 2 designates thefurnace generally, and 1 designates the drying chamber. The furnace isdivided into a preheating zone 2*, a hot zone 2 and a cooling zone 2,these zones corresponding to the similar zones of the structure shown inFigure 1.

At each side of the hot zone 2 are radiating combustion chambers, whichmay be of the single flue type 9* or of the double flue type 9 Thesecombustion chambers are adapted to radiate heat directly into thefurnace space within the hot zone 2 and the products of combustionthere-' from are delivered to a bottom flue 10 As previously pointed outin connection with the structure shown in Figure 1, fuel may also beburned in the bottom fiue. The bottom flue 10 is shown as having-twomain passages between which is open brickwork 10 The fioor of thefurnace chamber 10 is preferably of silicon carbide or other refractorymaterial which is a good conductor of heat and a good heat radiatingmaterial. The bottom flue 10 extends forwardly under the preheating zone2'. By this arrangement the preheating of the ware in the zone 2 is morerapidly effected.

At the forward end of the bottom flue 10 is a transverse passage 10 thatcommunicates with a flue 10 located under the drying oven 1*. The flue10 may extend entirely along the bottom of the oven 1 for the fulllength thereof and communicate with a stack 10 at the entrance end ofthe drying oven. By thus utilizing waste heat from the furnace to dryware in the oven, the pro,- vision of burners for heating the oven canbe done away with, or less fuel need be burned for heating the even ifburners are provided.

In certain types of enamel work the process is divided into more stepsthan has been described. here, in that the ware after being burned isagain coated and burned at the same or a different temperature.

In Figure 4 we have shown one modification of our invention whereinadditional furnace units are arranged to provide for successive burningof the ware. In this figure designates the continuous conveyor passingaround sheaves 21. Disposed along one reach of the conveyor are driers22 between which is a fusing chamber 23. Along the other reach of theconveyor are two fusing chambers 23 and a single drier 22. Thearrangement is such that there is a drier alongside each fusing chamberso as to permit the utilization of waste heat from the fusing chamber inthe adjacent drier. The construction of the fusing chambers is the sameas the construction of the fusing chamber 2 previously described, andthe construction of the drier corresponds to the construction of thedriers 1 previously described.

In Figure 5 we havedisclosed a further modification of our inventionwherein there is a single central fusing chamber or furnace 24 with adrier 25 on one side thereof and a drier 26 on the other side thereof.There are two separate conveyors 2'7 and 28. The conveyor 27 travelsthrough the fusing chamber 24 and the drier 26 and conveyor 28 travelsthrough the fusing chamber 24 and the drier 25. In this arrangement wehave shown that conveyors travel in opposite directions, as indicated bythe arrows, but such an arrangement is optional and the conveyors maytravel in the same direction through the furnace. Fuel economy iseffected and a saving of floor space is made possible by thisarrangement of a common fusing chamber and a drier at each side thereof.

From the foregoing it will be seen that in the arrangement illustratedthe general plan of our invention provides a drier tunnel and fusingchamber side by side in order that the heat may be efficiently utilized.It is not essential, how-. ever, that these be exactly side by side inorder to come within the spirit of our invention, but only that theyshall be so placed that ware shall pass through them'while carried on asingle conveyor common to the two tunnels.

As a further modification it is contemplated that instead of providing aslot in the top of the furnace, the top of the furnace may be closed andthe hangers with the conveyor can be located below the bottom of thefurnace chambers. One such arrangement is shown in Figure 9 wherein thefurnace 30 corresponding to a fusing chamber 2, is provided with acombustion chamber 31 at each side thereof in its central portion. Inthe roof of the furnace is a combustion chamber 31 corresponding to thecombustion chamber of the arrangement shown in Figure 2. Extending alongthe bottom of the furnace is a slot 32. In

suitable guides, pipes preferably being employed so as to permit of thecirculation of a cooling fluid therethrough. The hangers project upthrough the slot 32 and have overlapping plates 36 thereon arrangedsimilarly to the plates 12 previously described. and adapted to rideover the surface of the pipes 34. The hangers 35 project downinto apassage 36 along the bottom of the furnace. The conveyor chain 37travels along this space 36 and each of the hangers 35 is provided witha counterweight 38 for holding the hanger in a vertical position.

In place of a counterweight 38, each hanger may be provided with a guideroller 39, as shown in Figure 10, which roller isadapted to cooperatewith a guideway 40 extending along the passage 36, theconstruction'shown in Figure 10 otherwise being generally similar tothat shown in Figure 9.

The plates 12 and 36 not only serve to close the slot against theentrance of air into the furnace, but they also afford protection to'theconveyor chain by preventing direct contact of heated gases and vaporswith such chain, and serve to dissipate heat which would otherwise'beconducted to the conveyor chain.

With further reference to the construction shown in Figures 12 and 13,it will be noted that the top of the furnace is in the form of asuspended arch, the arch being suspended from the framework 45. Thecentral portion of the arch on each side of the slot, and designated 46,is hung from a member 47 that pivots on a part 48 of the metal frame.The pressure of this portion 551 of the arch, due to its pivotalsuspension, exerts a lateral pressure on the intermediate portion ofthe} arch to more firmly position the arch against the top of the sidewalls of the furnace. It will also be seen from an inspection of thesefigures that the conveyor travels through the drying oven, beingsuspended from the guide 3 located inside of the oven, but that theconveyor isv located outside and over the top of the furnace. Due tothelower temperature which exists in the oven, the conveyor may passentirely through the oven, and slotted construction need only be hefurnace. ave shown certain preferred embodiments' our invention, it willbe understood that various changes and modifications-may be made thereinwithin the contemplation of our invention andunder the scope of thefollowing claims. Furthermore, while we have specifically described theinvention as being applied to the a space 33 below the slot are pipes34, or other firing of enameled metal ware, it is obviously not confinedto such use. v

We claim:

1. In combination with a furnace chamber with slotted roof, a conveyortravelling above the roof and provided with a succession of hangersextending through the slot in the roof, successive, hangers carryingpivoted to them plates dof greater longitudinalextent than the intervalbetween hangers and of greater lateral extent than .the width of theslot, the portion of each plate to the rear of its pivot being heavierthan the portion to the front.

2. Apparatus of the class described, comprising an endless carrier forware, a drier, a fusing chamber, said carrier passing through the drierand the fusing chamber, and being; exposed be tween one end of the drierand one end of the fusing chamber.

3. Apparatus of the class described, comprising an endless carrier forware, a drier, a fusing chamber, said carrier passing through the drierand the fusing chamber, said carrier traveling in the open at each endof said chambers.

4. Apparatus of the class described,.comprising a drier and a fusingchamber, and a carrier passing through a drier and the fusing chamber,the conveyor being exposed between the drier and the fusing chamber andbetween the fusing chamber and the drier.

5. Apparatus of the class described, comprising a succession of drierand fusing chambers alternately arranged, and an endless conveyorassociated therewith and adapted to convey ware successivelytherethrough.

6. Apparatusof the class described. comprising a succession of drier andfusing chambers alternately arranged and spaced apart, and an endlesscarrier associated therewith and adapted to convey ware successivelytherethrough.

7. In a furnace, a furnace structure having a longitudinal slot in onewall thereof, a conveyor movable along the slot outside the furnace,supports on the conveyor projecting through the slot, said slot havingheat resistant rail members along each side thereof, and a verticallyselfadjustable plate on each support adapted to ride alongsaid rail incontact therewith to close the slot.

8. In 'a furnace, a furnace structure having a longitudinalslottherealong, heat resisting guides along each edge of the slot, atraveling conveyor outside the furnace movable along the slot, carrierson the conveyor projecting through the slot into the furnace, and plateson the conveyor adapted to rest on said guides and ride along the same,said plates being vertically freely movable relatively to the'conveyor.

9. In a furnace, a furnace structure having a longitudinal slottherealong, heat resisting guides along each edge of the slot, atraveling conveyor outside the furnace movable along the slot, carrierson the conveyor projecting through the slot into the furnace, andsubstantially flat overlapping plates on the conveyor adapted to rest onsaid guides and ride along the same, said plates being vertically selfadjustable relatively to the conveyor whereby they may ride up and downwith respect thereto to accommodate for irregularities in the guide.

10. In a furnace, a furnace structure having a longitudinal slottherealong, heat resisting guides along each edge of the slot, atraveling conveyor outside the furnace movable along the slot, carrierson the conveyor projecting through the slot 50 into the'furnace, andsubstantially fiat overlapping plates on the conveyor adapted to rest onsaid guides and ride along the same, at least one end of each platebeing freely movable vertically to adjust itself to the top of theguides.

11. In a furnace, a furnace structure having a longitudinal slottherealong, a conveyor located above the slot, rode on the conveyorprojecting through the slot into the furnace, and a series of platessuspended from the conveyor, the ends of adjacent plates overlapping, atleast one end of each plate being freely movable vertically, said platesbeing adapted to ride along the top of the furnace and cover the slot.

12. In a furnace, a furnace structure having a longitudinal slot in onewall thereof, a conveyor movable along the slot outside the furnace,supports on the conveyor projecting through the slot, said slot having aheat resistant rail along each side thereof, and a plate on each supportadapted to ride along said rail to close the slot the plates beingfreely movable vertically with respect to the conveyor whereby theymaintain themselves in contact with the rails, said plates being longerthan the distance between the supports and being pivotally mounted onthe supports.

13. In a furnace, a furnace structure having a slot in one wall thereof,a traveling conveyor outside the furnace movable along the slot andhaving conveyor elements projecting through the slot, the edges of theslot being paralleled by heat resistant water-cooled rails.

14. In a furnace, a furnace structure having a slot in one wall thereof,a traveling conveyor outside the furnace movable along the slot andhaving conveyor elements projecting through the slot, a water-cooledguide rail along each edge of the slot, and vertically adjustableoverlapping plates on the conveyor adapted to ride on the rails andclose the slot. l

15. In a furnace, a furnace structurehaving a suspended arch at the topthereof, said arch having a longitudinally extending slot therein, and aconveyor above the furnace structure having supporting elementsprojecting through the slot.

16. Apparatus of the class described, including a furnace structurehaving a slot therealong, said furnace structure having a continuouspassage therethrough, a conveyor located outside the passage in thefurnace and having hangers which project through the slot into thepassage, rails along each edge of the slot, and closure plates on saidsupports freely movable vertically thereon adapted to ride on said railsin contact therewith, said plates overlapping one another and serving tosubstantially close the slot in the furnaceand protect the main portionof the conveyor from exposure to the direct heat in the furnace passage.

1'7. In an enameling apparatus, a kiln hav ing a firing zone and apre-heating zone, a flue leading from the firing zone along thepre-heattal endless carrier having oppositely moving parallel reaches, adrying chamber. along which one reach passes, a fluxing chamber'abovethetop of which the other reach passes, the top of the fluxing chamberbeing slotted longitudinally, and hangers suspended from the conveyorfor supporting Ware, said hangers extending through the slot in thefluxing chamber, means for heating the drier.

l9. Enameling apparatus comprising a horizontal endless carrier havingoppositely moving parallel reaches, ,a drying chamber along which onereach passes, a fluxing chamber above the top of which the other reachpasses, the top of the fiuxing chamber being slotted longitudinally, andhangers suspended from the conveyor for supporting ware, said hangersextending through the slot in the fiuxing chamber, and controllablemeans for heating the drier, the conveyor traveling in the openingbetween both ends of the fluxing chamber and the drier, therebyproviding access for placing ware on the conveyor at one end of thedrier after it has been clipped, and permitting access to the ware forbeading and inspection before it is fired and after it has been dried.

20. The combination with a furnace structure having a slot through thetop wall thereof, of' a track above the top wall of the furnacestructure, carriers on said track having load supporting membersdepending therefrom, said members extending through the slot into'theinterior of the furnace, the furnace having a bearing surface thereonalong each side of the slot, and vertically movable cover plates on saidmembers adapted to ride on said bearing surfaces and seal the slot, saidplates being free to move vertically with irregularities in the bearingsurface and thereby maintain the slot closed.

21. The combination with a furnace structure having a slot through thetop wall thereof, of a and controllable I track above the top wall ofthe furnace structure, carriers on said track having load supportingmembers depending therefrom, said members extending through the slotinto the interior of the furnace, the furnace having a bearing surfacethereon along each side of the slot, and vertically movable cover plateson said members adapted to ride on said bearing surfaces and seal theslot, said plates having a sliding engagement with the members wherebythey are free to adjust themselves vertically and accommodate for anyirregularities in the bearing surfaces, and means on said members forlimiting the downward movement of the plates.

22. In a furnace, a furnace structure having a longitudinal slottherealong, heat resisting guides along each edge of the slot, atraveling conveyor outside the furnace movable along the slot, carrierson the conveyors projecting through the L slot into the furnace,substantially fiat overlapping plates on the conveyor adapted to rest onsaid guides and ride along the same to seal the slot, at least one endof each plate being freely movable vertically to adjust itself to thetop of the guides and means for limiting the downward movement of saidplates on said carriers when not in contact with said guides.

23. In apparatus for heating enameled articles, a main furnace providedwith a continuous chamber having a zone of gradually increasingtemperature adapted to dry enamel and preheat the articles and a burningzone adapted to fuse the enamel, an auxiliary drying furnace parallelwith said main furnace, means commonto said furnaces for heating thesame, and an endless conveyor chain traversing said main furnace andsaid auxiliary furnace and having parallel reachesspaced to provide roomfor work stations for applying the unvitrified enamel coating bothwithin and without the loop of the chain.

24. In apparatus for heating enameled articles, a main furnace providedwith a continuous chamber having a zone of gradually increasing temperature adapted to dry enamel and preheatthe articles and a burningzone adapted to fuse the enamel, a combustion chamber for heating theburning zone, an auxiliary drying furnace parallel with the main furnaceand adapted to dry enamel, a flue passage communicating with saidcombustion chamber and having a portion extending longitudinally throughthe lower part of said auxiliary furnace, and an endless conveyor chainhaving opposite reaches arranged to trav- ,ing zone adapted to fuse theenamel on the articles, an auxiliary furnace associated with the mainfurnace and adapted to dry enamel on the articles, a conveyor chainarranged to traverse said auxiliary furnace and said zones of the mainfurnace, and driving means for actuating said chain.-

26. In apparatus 'for heating enameled ar-' ticles, a main furnacehaving a tunnel chamber adapted to dry enamel, preheat the articles andfuse the enamel as the articles travel ,therethrough, a. combustionchamber below said tunnel chamber, an auxiliary drying furnace parallelwith said main furnace, a fiuepassage communicating with said combustionchamber and having a portion extending longitudinally through the lowerpart of said auxiliary furnace, and an endless conveyor chain havingopposite reaches arranged to traverse said auxiliary furnace and thetunnel chamber of the main furnace and to convey the articlestherethrough.

27. In apparatus for heating enameled articles, a main furnace providedwith a tunnel chamber adapted to heat the articles and fuse the enamelthereon as the articles pass through the chamber, an auxiliary furnaceassociated with the main furnace and adapted to dry enamel on thearticles, a conveyor chain arranged to traverse said auxiliary furnaceand the tunnel chamber of the main furnace for conveying the articlestherethrough, and driving means for actuating said chain.

WILLIAM T. CHRIS'IMAN.

HERBERT DEAN.

